EVAL-AD8302-ARDZ

Greetings Alex,

AD8302 phase measurement uses the EX-OR method, as described on bottom of datasheet page 15. Because of this, there will be a phase ambiguity. The ambiguity is typified by the triangle shape of the phase response across 360 degrees, as shown in datasheet graphs TPC 25 to TPC 29. Typically the application will take this into account and incorporate a known provision to resolve the ambiguity. In many a basic application, the designer already knows which side of the triangle the circuit operates, thus determining which of the two equations below will apply. 

(1) Looking at datasheet TPC 25 for example, we can write the equation below to describe the left-hand side of the triangle response: 

        phase [degrees] = -180 + (VPHS * 100)

Similarly, we can write a similar equation to describe the right-hand side of the triangle response:

        phase [degrees] = 180 - (VPHS * 100)

Notice the rounding of the triangle response near the peaks. It means for best accuracy, the design should avoid these areas. The equations above assume linearity, and ignore the rounding. 

(2) There should be a small EEPROM on the AD8302-ARDZ board which a clever programmer could use to store the basic slope and offset coefficients for calibration. I don't think our factory demo supports such feature. In lieu of this technique, perhaps consider storing calibration coefficients elsewhere, such as in the Python code somewhere. 

Hope this helps.  -Bruce H. 

Hi Bruce,

Thanks you so much!

-Alex

Hi Bruce,

Thanks you so much!

-Alex